THE CHICKEN TRANSFORMING GROWTH FACTOR-BETA-3 GENE - GENOMIC STRUCTURE, TRANSCRIPTIONAL ANALYSIS, AND CHROMOSOMAL LOCATION

In this paper, we report the isolation, characterization, and mapping of the chicken transforming growth factor-beta 3 (TGF-beta 3) gene. Th e gene contains seven exons and six introns spanning 16-kb of the chic ken genome. A comparison of the 5'-flanking regions of human and chick en TGF-beta 3 genes reveals two regions of sequence conservation. The first contains ATF/CRE and TBP/TATA sequence motifs within an 87-bp re gion. The second is a 162-bp region with no known sequence motifs. Ide ntification of transcription start sites using chicken RNA isolated fr om various embryonic and adult tissues reveals two sites of initiation , P1 and P2, which map to these two conserved regions. Comparison of 3 '-flanking regions of chicken and mammalian TGF-beta 3 genes also reve aled conserved sequences, The most significant homologies were found i n the 3'-most end of the transcribed region. DNA sequence analysis of chicken TGF-beta 3 cDNAs isolated by 3'-RACE revealed multiple polyade nylation sites unusually distant from a poly(A) signal motif. A Mse I restriction fragment length polymorphism (RFLP) marker was used to map the TGFB3 locus to linkage group E7 on the East Lansing reference bac kcross. Linkage to the TH locus showed that the TGFB3 locus was physic ally located on chicken chromosome 5.